The invention relates to a method for the contactless transmission of data from a data carrier to a write/read station, wherein the write/read station generates a carrier signal and the generated carrier signal is applied to contactless operative transmitter means of the write/read station, wherein a carrier signal is obtained in the data carrier by means of contactless operative transmitter means of the data carrier which are coupled to the transmitter means of the write/read station in a contactless manner, wherein load modulation of the carrier signal is performed by means of one auxiliary carrier signal in a transmission mode for the transmission of a data block from the data carrier to the write/read station, wherein the carrier signal load modulated by means of the one auxiliary carrier signal is demodulated by means of demodulation means in the write/read station in order to obtain the transmitted data block, wherein a test is performed in the write/read station in order to determine whether disturbances occur in the signal path beyond the demodulation means, and wherein control information is generated upon detection of disturbances.
The invention also relates to a write/read station for the contactless reception of data from a data carrier, which station includes carrier signal generating means for generating a carrier signal and contactless operative transmitter means which can be supplied with the carrier signal and can be coupled to contactless operative transmitter means of the data carrier in a contactless manner so that a carrier signal can be obtained in the data carrier by means of the transmitter means of the data carrier, in which load modulation of the carrier signal can be performed by means of one auxiliary carrier signal in a transmission mode for the transmission of a data block from the data carrier to the write/read station, includes demodulation means for demodulating the carrier signal load modulated by means of the one auxiliary carrier signal, which demodulation means can output a data block transmitted from the data carrier to the write/read station, and includes test means which are arranged to test whether disturbances occur in the signal path beyond the demodulation means and to generate control information upon detection of disturbances.
The invention also relates to a data carrier for the contactless output of data to a write/read station, which data carrier includes contactless operative transmitter means which can be coupled to contactless operative transmitter means of the write/read station, where a carrier signal generated in the write/read station can be obtained in the data carrier in the coupled state, and also includes load modulation means whereby the carrier signal can be load modulated by means of one auxiliary carrier signal in a transmission mode for the transmission of a data from the data carrier to the write/read station.
The invention also relates to an integrated circuit for a data carrier for the contactless output of data to a write/read station, which circuit includes connection means for the connection of contactless operative transmitter means which can be coupled to contactless operative transmitter means of the write/read station, where a carrier signal generated in the write/read station can be obtained in the circuit in the coupled state, and also includes load modulation means whereby the carrier signal can be load modulated by means of one auxiliary carrier signal in a transmission mode for the transmission of a data block from the circuit to the write/read station.
In the context of the present invention reference is made to a data carrier system which is realized in many versions and is marketed by the present Applicant so that it is known. In addition to this known data carrier system, reference is made to the patent document U.S. Pat. No. 5,345,231, whose publication is incorporated herein by way of reference. In the known data carrier system a carrier signal which is generated in the write/read station and inductively obtained in the data carrier is subjected to load modulation by means of an auxiliary carrier signal in order to transmit digital data, i.e. data blocks, from a data carrier to a write/read station; the auxiliary carrier signal then has an auxiliary carrier frequency f1 of 423.75 kHz and the ratio of this auxiliary carrier frequency f1 to the carrier frequency f0 of the carrier signal amounts to an integer number. A xe2x80x9c0xe2x80x9d bit, for example, is then transmitted from the data carrier to the write/read station by load modulation of the carrier signal by means of the auxiliary carrier signal during the first bit half and by omission of load modulation of the carrier signal during the second bit half, whereas a xe2x80x9c1xe2x80x9d bit is transmitted from the data carrier to the write/read station by omission of load modulation of the carrier signal during the first bit half and by load modulation of the carrier signal by means of the auxiliary carrier signal during the second bit half. If at least one disturbance occurs during the execution of the data transmission from the data carrier to the write/read station, and hence, for example an error in the data transmission, such a disturbance is detected by means of test means which are included in the write/read station and are formed, for example by a logic circuit or a microcomputer or a CRC stage (Cross Redundancy Check stage); these test means generate control information upon detection of disturbances. In the known data carrier system this control information is used exclusively for indication purposes in order to draw the attention of a user of the data carrier system to a disturbed or incorrect operation. A user of the known data carrier system can then attempt to take steps so as to avoid the further occurrence of such disturbances. This is experienced as a nuisance which actually constitutes a shortcoming that cannot be eliminated by numerous users.
It is an object of the invention to avoid the described problems and to provide, in a simple manner and using simple means, an improved write/read station of the kind set forth in the second paragraph, an improved data carrier of the kind set forth in the third paragraph as well as an improved integrated circuit of the kind set forth in the fourth paragraph, so that application of these improved means enables execution of an improved method of the kind set forth in the first paragraph.
In order to achieve the described object a method of the kind set forth in the first paragraph according to the invention is characterized in that at least one transmission mode data block is generated as control information, that the transmission mode data block is transmitted to the data carrier, that the transmitted transmission mode data block is evaluated in the data carrier and that, in conformity with the evaluation of the transmitted transmission mode data block, the data carrier is controlled to an other transmission mode in which, in order to transmit a data block from the data carrier to the write/read station, load modulation of the carrier signal is performed by means of at least one other auxiliary carrier signal, the at least one frequency of the at least one other auxiliary carrier signal and the frequency of the one auxiliary carrier signal having different values.
In order to achieve the described object a write/read station of the kind set forth in the second paragraph according to the invention is characterized in that the test means are arranged to generate at least one transmission mode data block as control information whereby in the data carrier an other transmission mode can be activated in which load modulation of the carrier signal can be performed by means of at least one other auxiliary carrier signal in order to transmit a data block from the data carrier to the write/read station, the at least one frequency of the at least one other auxiliary carrier signal and the frequency of the one auxiliary carrier signal having different values.
In order to achieve the described object a data carrier of the kind set forth in the third paragraph according to the invention is characterized in that the data carrier includes evaluation means for evaluating a transmission mode data block which is transmitted to the data carrier by the write/read station and can control the data carrier to an other transmission mode in which load modulation of the carrier signal by means of at least one other auxiliary carrier signal can be performed in order to transmit a data block from the data carrier to the write/read station, and that the data carrier includes control means which can be influenced by the evaluation means and whereby the data carrier can be controlled, in conformity with an evaluated transmission mode data block, to an other transmission mode in which, in order to transmit a data block from the data carrier to the write/read station, load modulation of the carrier signal can be performed by means of at least one other auxiliary carrier signal, the at least one frequency of the at least one other auxiliary carrier signal and the frequency of the one auxiliary carrier signal having different values.
In order to achieve the described object an integrated circuit of the kind set forth in the fourth paragraph according to the invention is characterized in that the circuit includes evaluation means for evaluating a transmission mode data block which is transmitted to the circuit by the write/read station and can control the circuit to an other transmission mode in which load modulation of the carrier signal can be performed by means of at least one other auxiliary carrier signal in order to transmit a data block from the circuit to the write/read station, and that the circuit includes control means which can be influenced by the evaluation means and whereby the circuit can be controlled, in conformity with an evaluated transmission mode data block, to an other transmission mode in which, in order to transmit a data block from the circuit to the write/read station, load modulation of the carrier signal can be performed by means of at least one other auxiliary signal, the at least one frequency of the at least one other auxiliary carrier signal and the frequency of the one auxiliary carrier signal having different values.
Using very few additional means, the steps according to the invention simply ensure that, after the detection of an error in the data transmission from a data carrier according to the invention to a write/read station according to the invention, the write/read station can influence the data carrier, that is to say in such a manner that, instead of a data transmission by load modulation of a carrier signal by means of one auxiliary carrier signal, switching over to a data transmission by load modulation of a carrier signal by means of at least one other auxiliary carrier signal takes place. In other words, the data transmission from a data carrier according to the invention to a write/read station according to the invention is enabled in one transmission mode by load modulation of a carrier signal by means of one auxiliary carrier signal and in other transmission modes by load modulation of a carrier signal by means of at least one other auxiliary carrier signal. In an other transmission mode load modulation of the carrier signal can be advantageously performed by means of only the other auxiliary carrier signal. In an other transmission mode, however, load modulation of the carrier signal can also be advantageously performed by means of the one auxiliary carrier signal and the other auxiliary carrier signal. In an other transmission mode, however, load modulation of the carrier signal can also be performed by means of two other, three other or four other auxiliary carrier signals. The use of one auxiliary carrier signal is advantageous, for example when disturbances occur in the range of the one auxiliary carrier signal but no disturbances occur in the range of the other auxiliary carrier signal, because load modulation of the carrier signal by means of the other auxiliary carrier signal then enables undisturbed and correct data transmission. The use of, for example two auxiliary carrier signals offers the advantage that, in the case of disturbances in the range of the one auxiliary carrier signal, it may be that no disturbances occur in the range of the other auxiliary carrier signal, so that data reception in the write/read station is then possible on the basis of the other auxiliary carrier signal. The use of two auxiliary carrier signals thus introduces a given redundancy which yields a high reliability. On the other hand, the use of two auxiliary carriers implies a comparatively high power consumption in a data carrier, so that its range is reduced. The use of only one auxiliary carrier signal for data transmission offers the advantage of a comparatively low power consumption in the data carrier; this is attractive with a view to achieving an as large as possible range. Due to the influencing of the data carrier by the write/read station, taking place upon detection of disturbances in the course of a data transmission from the data carrier to the write/read station, it is advantageously possible to activate each time a more attractive transmission mode or communication mode for a data carrier according to the invention.
It is to be noted that for the transmission of digital data, i.e. data blocks, from a data carrier to a write/read station it is already known from the patent document EP 0 845 751 A1 to subject a carrier signal which is generated in the write/read station and inductively obtained in the data carrier to load modulation by means of two auxiliary carrier signals, the ratio of the auxiliary carrier frequencies f1 and f2 of the auxiliary carrier signals to the carrier frequency f0 of the carrier signal each time being an integer number. A xe2x80x9c1xe2x80x9d bit is then transmitted by load modulation of the carrier signal by means of the auxiliary carrier signal having the frequency f1=484.2 kHz and a xe2x80x9c0xe2x80x9d bit is transmitted by load modulation of the carrier signal by means of the auxiliary carrier signal having the auxiliary carrier frequency f2=423.75 kHz. When disturbances occur in the data transmission from the data carrier to the write/read station, they are detected by the test means included in the write/read station, after which the test means generate control information upon detection of disturbances or errors in the received data. This control information is applied to sequencing means which output, in dependence on the supplied control information, switching signals which are used for switching purposes within the write/read station; via these switching operations it is attempted to achieve an improved or an essentially correct data transmission. In the data carrier system which is known from the patent document EP 0 845 751 A1, upon detection of disturbances or errors in the data transmission switching operations are carried out only in the write/read station. Such switching operations, however, cannot have an effect on disturbances whose origins lie in the transmission path from the data carrier to the write/read station, so that errors caused by such disturbances during the data transmission cannot be eliminated in this known data carrier system.
These and other aspects of the invention will become apparent from the embodiment described hereinafter.